1. Field
Example embodiments herein relate to semiconductor devices and methods of forming the same, and more particularly, to semiconductor memory devices and methods of forming the same.
2. Related Art
Semiconductor devices are generally recognized as important devices in the electronic industry, because semiconductor devices have characteristics such as multi-functions and/or low manufacturing costs. Semiconductor memory devices are semiconductor devices capable of storing logic data and reading stored data. Semiconductor memory devices can broadly be classified as volatile memory devices or non-volatile memory devices. A volatile memory device retains no stored data when power supply is stopped. A DRAM device and an SRAM device are representative volatile memory devices. On the contrary, a non-volatile memory device retains stored data even when power supply is stopped. A flash memory device is a representative non-volatile memory device.
With the increasing developments in the electronic industry, semiconductor memory devices are required to have a larger capacity. Therefore, the semiconductor memory devices have a tendency to be more highly-integrated. Due to various problems, however, it is difficult to realize highly-integrated semiconductor memory devices. For example, a photolithography process for defining minute patterns has limits. Because it is difficult to reduce the occupied area of the minute patterns, the ability to realize more highly-integrated semiconductor devices is restricted. In order to solve these problems, more studies are being carried out to realize highly-integrated semiconductor memory devices.